1. Field of the Invention
The present invention relates generally to devices for treating surfaces which project an abrading material toward a surface to be treated and more particularly, but without limitation, to automated, portable devices for treating such surfaces.
2. Discussion
Man has developed a wide variety of surfaces and surface treatments for use in a variety of environments. For instance, many business, such as machine shops, manufacturing facilities and a wide variety of others have concrete floors which, over time, may develop a soiled and stained appearance. It is often desirable to resurface the concrete floor. Or perhaps the concrete floor has been painted or given some other surface treatment. Many times it is desirable to remove the paint or surface treatment so that a new surface treatment can be applied. Yet another example is a parking lot that has lines painted on it to facilitate organization of the parking on the surface. It is sometimes desirable to remove the painted on lines and reorganize the parking lot by providing new lines. These are but a few of the great number of surfaces and surface treatments that require maintenance and renovation.
Various devices have been developed to assist in treating these surfaces. For example, U.S. Pat. No. 4,377,922 and U.S. Pat. No. 5,142,831 are somewhat typical of such devices. Each of these prior art devices provide a portable apparatus which includes a centrifugal blast wheel which projects an abrading material, such as steel shot or the like, through a blast corridor onto the surface to be treated. The rebounding abrading material along with any dust or particulate resulting from the treatment of the surface are collected using a rebound corridor and vacuum source. The abrading material is separated from the dust and other particulate and recycled to a hopper which supplies the abrading material to the centrifugal blast wheel.
Although such prior art devices have been useful in treating surfaces, these devices have been fraught with numerous drawbacks and deficiencies. For instance, prior art machines have typically utilized a valve located between the hopper and the centrifugal blast wheel to control the rate of flow of particulate material. This valve has, in the past, been controlled manually and is a very awkward and imprecise. Thus, during use an operator is required to steer the device, control the rate of progression of the device and control the flow of abrading material to ensure a uniform treatment of the surface. These functions often must be simultaneously, making it very difficult to obtain a uniform treatment. This is especially true if the operator has little or no experience using the device.
Even for an experienced operator, prior art devices have been particularly difficult to obtain uniform results at startup and shut down, because the blast intensity has not been adjusted to the rate of forward progression of the device. Once the power cord has been disconnected from prior art machines, these machines have been difficult to move and maneuver without supplying power to the drive system.
Another drawback of prior art machines has been a lack of safety features. Many such devices could provide serious harm to the operator or others because the abrading material can be feed to the centrifugal blast wheel while the device is being repaired, moved and even when the device is tipped on its side.
Thus, while prior art surface treatment devices are known, there remains a need for an improved device which does not suffer from the drawbacks of currently available devices.